JP2012150381A - Projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projector capable of sufficiently enhancing contrast by suppressing an occurrence of a black floating as much as possible.SOLUTION: A projector 1 according to the present invention comprises: an illuminating device 2 emitting a plurality of color light beams; a plurality of liquid crystal light valves 11R, 11G and 11B being a reflection type of a vertical alignment mode and modulating individual color light beams; a retardation compensation plate 12 including a C plate and an O plate disposed between the illuminating device 2 and the plurality of liquid crystal light valves 11R, 11G and 11B; a color synthesizing element 4 synthesizing the color light beams having been modulated; and a projection optical system 5 projecting light having been synthesized on a projection surface to be projected. A transverse plane phase difference value of the retardation compensation plate 12 corresponding to at least one of the plurality of liquid crystal light valves 11R, 11G and 11B is different from a transverse plane phase difference value of the retardation compensation plate 12 corresponding to other liquid crystal light valves 11R, 11G and 11B.

Description

  The present invention relates to a projector.

  In recent years, a projector having a vertical alignment (hereinafter sometimes abbreviated as VA) mode liquid crystal light valve has been proposed as having excellent contrast when viewed from the front. A VA mode liquid crystal light valve is obtained by sandwiching a liquid crystal layer having negative dielectric anisotropy between a pair of substrates and aligning liquid crystal molecules substantially vertically in a state where no voltage is applied. However, even when such a VA mode liquid crystal light valve is used, the contrast is lowered when viewing from an oblique direction, and the display quality is lowered.

  Therefore, conventionally, a phase difference of light passing obliquely through the liquid crystal layer is compensated by using a phase difference compensation element having an optical axis along the thickness direction, a so-called C plate. At this time, the C plate is tilted so that the optical axis of the C plate is parallel to the pretilt direction of the liquid crystal molecules, so that the front phase difference of the liquid crystal is compensated by the C plate. In this case, a jig for arranging the C plate in an inclined posture is required.

  However, when the positional deviation of the inclination jig (inclination angle deviation) or the azimuth angle deviation of the liquid crystal alignment occurs, sufficient phase difference compensation cannot be performed only by inclining the C plate. Further, when the cell thickness of the liquid crystal panel varies, it is necessary to adjust the front phase difference of the liquid crystal panel with respect to the cell thickness change by the inclination angle of the C plate. However, in this case, the effective retardation of the C plate deviates from the optimum condition, and sufficient phase difference compensation cannot be performed. Further, as the pretilt angle of the liquid crystal molecules increases, the tilt angle of the C plate also increases. At this time, however, the difference in reflectance between P-polarized light and S-polarized light occurs with respect to incident polarized light, and the axis of incident polarized light is shifted. Decreases the contrast.

  In view of this, it has been proposed to increase the contrast by performing higher phase difference compensation using a so-called O plate having a biaxial refractive index anisotropy in addition to such a C plate. For example, see Patent Document 1).

JP 2009-145862 A

  In the projector described in Patent Document 1, a C plate and an O plate are arranged on the light emission side of the liquid crystal panel. However, if the C plate and the O plate are simply arranged on the light emission side of the liquid crystal panels for red light modulation, green modulation, and blue modulation, a phenomenon that the black display is slightly brightened, so-called black floating occurs. The contrast cannot be improved sufficiently.

  SUMMARY An advantage of some aspects of the invention is that it provides a projector capable of sufficiently improving contrast by suppressing the occurrence of black float as much as possible.

  In order to achieve the above object, a projector according to the present invention includes an illumination device that emits a plurality of color lights of different colors, and a plurality of reflective liquid crystal light valves in a vertical alignment mode that modulates each of the plurality of color lights. A first retardation compensation layer provided between the illumination device and each of the liquid crystal light valves, the optical axis of which has a negative uniaxial refractive index anisotropy along the thickness direction, and biaxiality A phase difference compensation plate including a second phase difference compensation layer having a refractive index anisotropy, a color synthesis optical system for synthesizing color light modulated by the plurality of liquid crystal light valves, and the color synthesis optical system. A projection optical system that projects the combined light onto the projection surface, and among the plurality of liquid crystal light valves, the front phase difference value of the phase difference compensation plate corresponding to at least one liquid crystal light valve is Compatible with other liquid crystal light valves Wherein wherein the front retardation value of the phase difference compensating plate different from that.

  In projectors equipped with multiple liquid crystal light valves that modulate different colors of light, the conditions such as the front phase difference value of the phase difference compensation plate and the arrangement of the optical axes are optimized for any one liquid crystal light valve. In general, other liquid crystal light valves are also adapted to this. However, since the wavelength of the light modulated by each liquid crystal light valve is different and the chromatic dispersion is different between the liquid crystal and the phase difference compensator, it is impossible to perform optimum phase difference compensation for all liquid crystal light valves. there were. For this reason, black floating occurs in liquid crystal light valves other than the liquid crystal light valve that is the standard to be optimized, resulting in a problem that the contrast of the image obtained from the combined light after combining each color light is lowered.

  In contrast, in the projector of the present invention, the front phase difference value of the phase difference compensation plate corresponding to at least one liquid crystal light valve among the plurality of liquid crystal light valves is set to the phase difference value corresponding to the other liquid crystal light valves. It is different from the front phase difference value of the compensation plate. As a result, optimal phase difference compensation can be performed for all the liquid crystal light valves, occurrence of black float can be suppressed, and contrast can be improved.

  In the projector according to the aspect of the invention, the plurality of liquid crystal light valves may be a red light modulation liquid crystal light valve, a green light modulation liquid crystal light valve, and a blue light modulation liquid crystal light valve. The front phase difference value of the corresponding phase difference compensation plate is larger than the front phase difference value of the phase difference compensation plate corresponding to the green light modulation liquid crystal light valve, and corresponds to the blue light modulation liquid crystal light valve. It is preferable that the front phase difference value of the phase difference compensation plate is smaller than the front phase difference value of the phase difference compensation plate corresponding to the green light modulating liquid crystal light valve.

  The wavelength dispersion of the liquid crystal layer of the liquid crystal light valve has a characteristic that the front phase difference is large on the long wavelength side and the front phase difference is small on the short wavelength side. Therefore, the front phase difference value of the phase difference compensation plate for red light is larger than the front phase difference value of the phase difference compensation plate for green light, and the front phase difference value of the phase difference compensation plate for blue light is for green light. If the configuration is smaller than the front phase difference value of the phase difference compensation plate, optimum phase difference compensation can be performed for all liquid crystal light valves.

  Another projector of the present invention includes an illumination device that emits a plurality of color lights of different colors, a plurality of reflective liquid crystal light valves in a vertical alignment mode that modulates each of the plurality of color lights, and each of the illumination devices and A first retardation compensation layer having a uniaxial negative refractive index anisotropy and a biaxial refractive index anisotropy provided between the liquid crystal light valve and an optical axis along the thickness direction. A phase difference compensation plate including two phase difference compensation layers, a color synthesis optical system that synthesizes color light modulated by the plurality of liquid crystal light valves, and light synthesized by the color synthesis optical system on a projection surface. A projection optical system, and the azimuth angle of the slow axis in the in-plane direction of the phase difference compensation plate corresponding to at least one liquid crystal light valve among the plurality of liquid crystal light valves is other liquid crystal light. Said phase corresponding to the valve Characterized in that differ from the azimuth of the slow axis in the in-plane orientation of the compensation plate.

  In another projector of the present invention, the azimuth angle of the slow axis viewed from the thickness direction of the retardation compensation plate corresponding to at least one liquid crystal light valve among the plurality of liquid crystal light valves is different from that of the other liquid crystal light valve. Is different from the azimuth angle of the slow axis as seen from the thickness direction of the phase difference compensation plate corresponding to. As a result, optimal phase difference compensation can be performed for all the liquid crystal light valves, occurrence of black float can be suppressed, and contrast can be improved.

  In the projector according to the aspect of the invention, the plurality of liquid crystal light valves are a red light modulation liquid crystal light valve, a green light modulation liquid crystal light valve, and a blue light modulation liquid crystal light valve, and the illumination device and the phase difference compensation plate Is provided with a polarization beam splitter having a predetermined transmission axis, and an angle formed between the slow axis and the transmission axis of the retardation compensation plate corresponding to the liquid crystal light valve for red light modulation is The phase difference compensator corresponding to the blue light modulating liquid crystal light valve is larger than an angle formed by the slow axis and the transmission axis of the phase difference compensating plate corresponding to the green light modulating liquid crystal light valve. An angle formed between the slow axis and the transmission axis is smaller than an angle formed between the slow axis and the transmission axis of the retardation compensation plate corresponding to the green light modulating liquid crystal light valve. Configuration is preferred.

  The angle between the slow axis of the phase difference compensator and the transmission axis of a polarized beam splitter (hereinafter abbreviated as PBS) is usually set to a small angle of about 0 to 10 degrees. .

1 is a schematic configuration diagram illustrating a projector according to a first embodiment of the invention. It is a perspective view which shows the structure of the liquid crystal light valve periphery of a projector. It is sectional drawing of the triangular prism unit holding a liquid crystal light valve. It is sectional drawing which shows schematic structure of a liquid crystal light valve. (A)-(C) are sectional drawings which show schematic structure of a phase difference compensating plate. (A) is a schematic diagram for demonstrating the optical anisotropy of C plate, (B) is a schematic diagram for demonstrating the optical anisotropy of O plate. It is a figure which shows the relationship of the optical axis arrangement | positioning of each component of an image forming optical system. It is a figure which shows the Poincare sphere for demonstrating the principle of this invention. It is the front view which looked at said Poincare sphere from S1 axis direction, and is a figure which shows the change of the polarization state of the light on a Poincare sphere when the front phase difference value of a phase difference compensator is changed. It is a figure which shows the change of the polarization state of the light on the Poincare sphere in the phase difference compensator for red light, (A) When not optimized, (B) The case where it optimizes is each shown. It is a figure which shows the change of the polarization state of the light on the Poincare sphere in the phase difference compensating plate for blue light, (A) When not optimized, (B) The case where it optimizes is each shown. In the projector according to the second embodiment of the present invention, the Poincare sphere is viewed from the S1 axis direction, and the polarization of light on the Poincare sphere when the slow axis angle of the phase difference compensator is changed. It is a figure which shows the change of a state. It is a figure which shows the change of the polarization state of the light on the Poincare sphere in the phase difference compensator for red light, (A) When not optimized, (B) The case where it optimizes is each shown. It is a figure which shows the change of the polarization state of the light on the Poincare sphere in the phase difference compensating plate for blue light, (A) When not optimized, (B) The case where it optimizes is each shown.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
In the present embodiment, a projector having three reflective liquid crystal light valves, that is, a so-called three-plate liquid crystal projector will be described as an example.
FIG. 1 is a schematic configuration diagram illustrating a projector according to the present embodiment. FIG. 2 is a perspective view showing a configuration around the liquid crystal light valve of the projector. FIG. 3 is a cross-sectional view of the triangular prism unit that holds the liquid crystal light valve.
It should be noted that in all of the following drawings, in order to make each component easy to see, the scale of dimensions may be different depending on the component.

  As shown in FIG. 1, the projector 1 according to this embodiment includes a lighting device 2 that emits three colors of light including red light (R light), green light (G light), and blue light (B light), and each color. Three sets of image forming optical systems 3R, 3G, and 3B that form images by light, a color combining element 4 (color combining optical system) that combines three colors of light, and a projected surface such as a screen And a projection optical system 5 for projecting to (not shown). The illumination device 2 includes a light source 6, an integrator optical system 7, and a color separation optical system 8. The image forming optical systems 3R, 3G, and 3B include an incident-side polarizing plate 9, a PBS 10, a reflective liquid crystal light valve 11R, 11G, and 11B, a phase difference compensating plate 12, and an exit-side polarizing plate 13. ing.

The projector 1 generally operates as follows.
White light emitted from the light source 6 enters the integrator optical system 7. The white light incident on the integrator optical system 7 is emitted with uniform illuminance and with the polarization state aligned with a predetermined linearly polarized light. The white light emitted from the integrator optical system 7 is separated into R, G, and B color lights by the color separation optical system 8 and is incident on different sets of image forming optical systems 3R, 3G, and 3B for each color light. The color light incident on each of the image forming optical systems 3R, 3G, 3B becomes modulated light modulated based on the image signal of the image to be displayed. The three colors of modulated light emitted from the three sets of image forming optical systems 3R, 3G, and 3B are combined by the color combining element 4 to become multicolor light and enter the projection optical system 5. The polychromatic light incident on the projection optical system 5 is projected onto a projection surface such as a screen. In this way, a full color image is displayed on the projection surface.

Hereinafter, each component of the projector 1 will be described in detail.
The light source 6 includes a light source lamp 15 and a parabolic reflector 16. The light emitted from the light source lamp 15 is reflected in one direction by the parabolic reflector 16 to become a substantially parallel light beam, and enters the integrator optical system 7 as light source light. The light source lamp 15 is composed of, for example, a metal halide lamp, a xenon lamp, a high-pressure mercury lamp, a halogen lamp, or the like. Instead of the parabolic reflector 16, an elliptical reflector, a spherical reflector, or the like may be used. A collimating lens that collimates the light emitted from the reflector may be used according to the shape of the reflector.

  The integrator optical system 7 includes a first lens array 17, a second lens array 18, a polarization conversion element 19, and a superimposing lens 20. The first lens array 17 has a plurality of microlenses 21 arranged on a surface substantially orthogonal to the optical axis L1 of the light source 6. Similar to the first lens array 17, the second lens array 18 has a plurality of microlenses 22. The microlenses 21 and 22 are arranged in a matrix, and the planar shape in a plane orthogonal to the optical axis L1 is similar to the illuminated area of the liquid crystal light valves 11R, 11G, and 11B (substantially rectangular). . The illuminated area is an area in which a plurality of pixels are arranged in a matrix in the liquid crystal light valves 11R, 11G, and 11B and contribute substantially to display.

  The polarization conversion element 19 has a plurality of polarization conversion units 23. Each polarization conversion unit 23 has a polarization separation film (hereinafter referred to as a PBS film), a ½ phase plate, and a reflection mirror, although its detailed structure is not shown. Each microlens 21 of the first lens array 17 has a one-to-one correspondence with each microlens 22 of the second lens array 18. Each micro lens 22 of the second lens array 18 has a one-to-one correspondence with each polarization conversion unit 23 of the polarization conversion element 19.

  The light source light incident on the integrator optical system 7 is spatially divided and incident on the plurality of microlenses 21 of the first lens array 17 and is collected for each light beam incident on the microlens 21. The light source light collected by each microlens 21 forms an image on the microlens 22 of the second lens array 18 corresponding to the microlens 21. That is, a secondary light source image is formed on each of the plurality of microlenses 22 of the second lens array 18. The light from the secondary light source image formed on the microlens 22 enters the polarization conversion unit 23 corresponding to the microlens 22.

  The light incident on the polarization conversion unit 23 is separated into P-polarized light and S-polarized light with respect to the PBS film. One of the separated polarized light (for example, S-polarized light) is reflected by a reflection mirror and then passed through a half-phase plate, so that the polarization state is converted and aligned with the other polarized light (for example, P-polarized light). Here, the polarization state of the light that has passed through the polarization conversion unit 23 is aligned with the polarization state that is transmitted through the incident-side polarizing plate 9 described later. Light emitted from the plurality of polarization conversion units 23 is superimposed on the illuminated areas of the liquid crystal light valves 11R, 11G, and 11B by the superimposing lens 20. The luminous fluxes spatially divided by the first lens array 17 illuminate substantially the entire illuminated area, whereby the illuminance distribution is averaged and the illuminance on the illuminated area is made uniform.

  The color separation optical system 8 includes a first dichroic mirror 25, a second dichroic mirror 26, a third dichroic mirror 27, a first reflection mirror 28, and a second reflection mirror 29 having a wavelength selection surface. The first dichroic mirror 25 has a spectral characteristic that reflects the red light LR and transmits the green light LG and the blue light LB. The second dichroic mirror 26 has a spectral characteristic that transmits the red light LR and reflects the green light LG and the blue light LB. The third dichroic mirror 27 has a spectral characteristic that reflects the green light LG and transmits the blue light LB. The first dichroic mirror 25 and the second dichroic mirror 26 are configured such that each wavelength selection surface is substantially orthogonal to each other, and each wavelength selection surface forms an angle of about 45 ° with the optical axis L2 of the integrator optical system 7. Are arranged as follows.

  The red light LR, the green light LG, and the blue light LB contained in the light source light incident on the color separation optical system 8 are separated as follows, and the image forming optical systems 3R, 3G, Incident on 3B. That is, the red light LR is transmitted through the second dichroic mirror 26, reflected by the first dichroic mirror 25, then reflected by the first reflecting mirror 28, and enters the red light image forming optical system 3R. The green light LG is transmitted through the first dichroic mirror 25, reflected by the second dichroic mirror 26, then reflected by the second reflecting mirror 29, reflected by the third dichroic mirror 27, and image forming optical system for green light Incident to 3G. The blue light LB is transmitted through the first dichroic mirror 25, reflected by the second dichroic mirror 26, then reflected by the second reflective mirror 29, and transmitted through the third dichroic mirror 27, thereby forming an image forming optical system for blue light. Incident on 3B. Each color light modulated by each image forming optical system 3R, 3G, 3B is incident on the color composition element 4.

  The color synthesizing element 4 is constituted by a dichroic prism. The dichroic prism has a structure in which four triangular prisms are bonded to each other. The surface to be bonded in the triangular prism becomes the inner surface of the dichroic prism. On the inner surface of the dichroic prism, a mirror surface that reflects red light LR and transmits green light LG and a mirror surface that reflects blue light LB and transmits green light LG are formed orthogonal to each other. The green light LG that has entered the dichroic prism travels straight through the mirror surface and is emitted. The red light LR and the blue light LB incident on the dichroic prism are selectively reflected or transmitted by the mirror surface and emitted in the same direction as the emission direction of the green light LG. In this way, the three color lights (images) are superimposed and synthesized, and the synthesized color lights are enlarged and projected onto the screen 7 by the projection optical system 5. The projection optical system 5 has a first lens group 44 and a second lens group 45.

  In the case of this embodiment, as shown in FIG. 2, the red light image forming optical system 3R, the green light image forming optical system 3G, and the blue light image forming optical system 3B are all unitized. It is configured. The unitized three image forming optical systems 3R, 3G, 3B are joined to the three light incident surfaces of the color synthesizing element 4.

Here, as a representative of the image forming optical system, the configuration of the green light image forming optical system 3G will be described.
As shown in FIG. 3, the green light image forming optical system 3G includes an incident side polarizing plate 9, a PBS 10, a green light liquid crystal light valve 11G, a phase difference compensation plate 12, an exit side polarizing plate 13, It has. Among these components, except for the incident-side polarizing plate 9, the PBS 10, the green light liquid crystal light valve 11G, the phase difference compensation plate 12, and the emission-side polarizing plate 13 are fixed to a casing 50 having a substantially triangular prism shape. Has been. The casing 50 is made of a material having high thermal conductivity such as aluminum.

  The three side surfaces 50a, 50b, and 50c of the housing 50 are provided with openings 50at, 50bt, and 50ct, respectively, through which light passes. Of the three side surfaces 50a, 50b, and 50c of the housing 50, two surfaces that are in contact with each other at right angles are a first side surface 50a and a second side surface 50b, and an angle of 45 ° with respect to the first side surface 50a and the second side surface 50b. Let the surface which touches be 3rd side surface 50c. The green light liquid crystal light valve 11G is fixed to the outer surface side of the first side surface 50a so as to close the opening 50at, and the phase difference compensation plate 12 is fixed to the inner surface side of the first side surface 50a so as to close the opening portion 50at. Has been. The exit side polarizing plate 13 is fixed to the outer surface side of the second side surface 50b so as to close the opening 50bt. The PBS 10 is fixed to the outer surface side of the third side surface 50c so as to close the opening 50ct. With such a configuration, the inside of the housing 50 is a sealed space.

  In the green light image forming optical system 3 </ b> G, the green light LG separated from the light source light enters the incident-side polarizing plate 9. The incident-side polarizing plate 9 transmits linearly polarized light that vibrates in a predetermined direction, and the transmission axis is set so as to transmit P-polarized light with respect to the polarization separation surface of the PBS 10 described below. Hereinafter, P-polarized light with respect to the polarization separation surface of the PBS 10 is simply referred to as P-polarization, and S-polarization with respect to the polarization separation surface of the PBS 10 is simply referred to as S-polarization. As described above, since the light source light that has passed through the integrator optical system 7 has the polarization state aligned with the P-polarized light, almost all of the green light LG passes through the incident-side polarizing plate 9 and enters the PBS 10.

  The PBS 10 of this embodiment is a wire grid type PBS, and is composed of, for example, a glass substrate and a plurality of metal wires formed thereon (not shown). The plurality of metal wires all extend in one direction (Z direction) and are formed on the glass substrate so as to be spaced apart from each other substantially in parallel. The main surface of the glass substrate on which the plurality of metal lines is formed is a polarization separation plane, the extending direction of the plurality of metal lines is the reflection axis direction, and the arrangement direction of the plurality of metal lines is the transmission axis direction. The polarization separation surface forms an angle of approximately 45 ° with respect to the central axis of the green light LG incident on the polarization separation surface. Of the green light LG incident on the polarization separation surface, S-polarized light whose polarization direction matches the reflection axis direction is reflected by the polarization separation surface, and P-polarized light whose polarization direction matches the transmission axis direction passes through the polarization separation surface. Since the green light LG is substantially P-polarized by the action of the polarization conversion element 19 and the incident-side polarizing plate 9 of the integrator optical system 7, almost all of the green light LG is transmitted through the polarization separation surface of the PBS 10 for green light. The light enters the liquid crystal light valve 11G. In addition, it is desirable that the incident-side polarizing plate 9 and the emission-side polarizing plate 13 are composed of wire grid type polarizing plates in consideration of heat resistance and the like.

  The green light liquid crystal light valve 11G of this embodiment is a reflective liquid crystal light valve, and the liquid crystal mode is a vertical alignment mode. As shown in FIG. 3, the green light liquid crystal light valve 11G includes a TFT array substrate 31 and a counter substrate 32 arranged to face each other, and a liquid crystal layer 33 sandwiched between the two substrates. Yes. The liquid crystal layer 33 is made of a liquid crystal material having a negative dielectric anisotropy.

  A phase difference compensation plate 12 is disposed on the optical path between the PBS 10 and the green light liquid crystal light valve 11G. The detailed configuration of the phase difference compensation plate 12 will be described later. The green light LG that has passed through the PBS 10 sequentially passes through the phase difference compensation plate 12 and the counter substrate 32 of the green light liquid crystal light valve 11G, enters the liquid crystal layer 33, and then is reflected and folded on the TFT array substrate 31. The green light LG is modulated while being transmitted through the liquid crystal layer 33 to become modulated light, and is transmitted again through the counter substrate 32 and the phase difference compensation plate 12.

  As shown in FIG. 4, a plurality of gate lines and a plurality of source lines are arranged on the substrate body 35 constituting the TFT array substrate 31 so as to be orthogonal to each other, and provided near the intersection of the gate lines and the source lines. A pixel electrode 36 is provided through the TFT. In FIG. 4, components such as gate lines, source lines, TFTs, and the like below the pixel electrode 36 are not shown. The pixel electrode 36 is made of a metal having a high light reflectance such as aluminum, silver, or an alloy thereof, and functions as a reflective electrode. On the other hand, a common electrode 39 made of a transparent conductive material such as indium tin oxide (hereinafter abbreviated as ITO) is provided on the substrate body 38 constituting the counter substrate 32.

An alignment film 37 is formed on the pixel electrode 36 of the TFT array substrate 31. Similarly, an alignment film 40 is formed on the common electrode 39 of the counter substrate 32. These alignment films 37 and 40 are formed by vacuum deposition of silicon oxide (SiO ₂ ). For example, the degree of vacuum during vacuum deposition is 5 × 10 ³ Pa, and the substrate temperature is 100 ° C. In order to impart anisotropy to the alignment films 37 and 40, vapor deposition is performed from a direction inclined by 45 degrees from the substrate surface. In this way, a silicon oxide column (columnar structure) grows in a direction inclined by 70 degrees from the substrate surface in the same direction as the deposition direction. The alignment film 37 on the TFT array substrate 31 and the alignment film 40 on the counter substrate 32 are arranged so that their alignment directions are antiparallel. Due to the alignment films 37 and 40, the liquid crystal molecules 33B of the liquid crystal layer 33 are aligned to form a predetermined pretilt angle. In the case where the work function difference between the material of the pixel electrode 36 and the material of the common electrode 39 causes flicker or image sticking, an insulating film may be provided between the pixel electrode 36 and the alignment film 37.

  As shown in FIG. 5A, the retardation compensation plate 12 has a C plate (negative C plate) 53 (first retardation compensation layer) formed on one surface of a quartz glass substrate 52, and the other. The O plate 54 (second phase difference compensation layer) is formed on the surface. That is, in this embodiment, the C plate 53 and the O plate 54 are integrated. The phase difference compensator 12 having such a structure is green so that the C plate 53 is located on the green light liquid crystal light valve 11G side and the O plate 54 is located on the opposite side of the green light liquid crystal light valve 11G. It is arranged in parallel with the light liquid crystal light valve 11G.

The C plate 53 is a multilayer film in which high refractive index layers and low refractive index layers are alternately laminated on the substrate 52 by sputtering or the like, and the optical axis is uniaxial negative refractive index difference along the thickness direction. It is a birefringent body having directionality. The C plate 53 has an optical axis perpendicular to the surface, and compensates for a phase difference of oblique light emitted from the green light liquid crystal light valve 11G. The high refractive index layer is made of TiO ₂ or ZrO ₂ which is a relatively high refractive index dielectric, and the low refractive index layer is made of SiO ₂ or MgF ₂ which is a low refractive index dielectric. In the C plate 53 having such a configuration, it is preferable that the thickness of each refractive index layer is thin in order to prevent the light passing therethrough from being reflected and interfering between the respective layers.

  FIG. 6A is a schematic diagram for explaining the optical anisotropy of the C plate 53. As shown by a refractive index ellipsoid in FIG. 6A, the relationship between the refractive indexes in each direction of the C plate 53 is nx = ny> nz, and the light incident in parallel to the optical axis of the C plate 53 Therefore, the phase difference cannot be compensated. In other words, the phase difference cannot be compensated for the light that enters the C plate 53 perpendicularly from the green liquid crystal light valve 11G. On the other hand, of the light emitted from the green light liquid crystal light valve 11G, the phase difference of the oblique component light, that is, the oblique component of the VA mode liquid crystal is optically compensated. Note that the C plate 53 does not have to completely satisfy nx = ny, and may have a slight phase difference. Specifically, the front phase difference value may be about 0 nm to 3 nm.

As this type of C plate 53, the thickness direction retardation Rth is preferably 100 nm or more and 300 nm or less, and more preferably 180 nm. Here, the thickness direction retardation Rth is defined by the following equation.
Rth = {(nx + ny) / 2−nz} × d
In the C plate 53 shown in FIG. 6A, nx and ny indicate the main refractive index in the surface direction, and nz similarly indicates the main refractive index in the thickness direction. D indicates the thickness of the C plate 53.

On the other hand, the O plate 54 is formed by obliquely vapor-depositing an inorganic material such as Ta ₂ O ₅ on the other surface of the quartz glass substrate 52 as shown in FIG. The O plate 54 has a film structure having columns (columnar structures) in which an inorganic material is grown along an oblique direction when viewed microscopically. An inorganic film having such a structure causes a phase difference due to its fine structure.

  FIG. 6B is a schematic diagram for explaining the optical anisotropy of the O plate 54. As shown by a refractive index ellipsoid in FIG. 6B, the O plate 54 is a birefringent body having a biaxial refractive index anisotropy in which the relationship between the refractive indexes in each direction is nx <ny <nz. is there. The O plate 54 has a slow axis due to the inorganic film in which the above-described column is formed. The slow axis of the O plate 54 coincides with an elliptical long axis 54c obtained by projecting the refractive index ellipsoid shown in FIG. 6B on the substrate (substrate surface) when viewed from the normal direction of the substrate.

  FIG. 7 is a diagram showing the relationship between the alignment direction of the liquid crystal molecules 33 </ b> B, the transmission axis of the PBS 10, and the slow axis of the O plate 54. As shown in FIG. 7, in this embodiment, when viewed from the direction along the optical axis, the angle α between the alignment direction of the liquid crystal molecules 33B and the transmission axis of the PBS 10 is 45 degrees, for example, and the transmission axis of the PBS 10 and the O plate An angle θ formed by 54 slow axes is set to 3 degrees, for example.

As described above, the red light image forming optical system 3R, the green light image forming optical system 3G, and the blue light image forming optical system 3B have the same basic configuration, but differ in the following portions.
That is, in the present embodiment, the front phase difference values of the O plate 54 of the phase difference compensating plate 12 in each of the image forming optical systems 3R, 3G, 3B are different. Specifically, the front phase difference value of the O plate 54 of the phase difference compensating plate 12 in the red light image forming optical system 3R is set to 15.4 nm, for example. The front phase difference value of the O plate 54 of the phase difference compensation plate 12 in the green light image forming optical system 3G is set to 15.0 nm, for example. The front phase difference value of the O plate 54 of the phase difference compensation plate 12 in the blue light image forming optical system 3B is set to, for example, 14.1 nm.

The front phase difference value Re is defined by the following equation.
Re = (nx−ny) × d
However, nx and ny indicate the main refractive index in the surface direction in the O plate 54 shown in FIG. D indicates the thickness of the O plate 54.

Here, the principle of phase difference compensation by the phase difference compensation plate 12 will be described using the Poincare sphere shown in FIG.
The linearly polarized light incident on the point A, which is the intersection of the Poincare sphere axis S1 and the sphere surface, passes through the O plate 54 and moves to the point B to become, for example, clockwise elliptically polarized light. Next, when the clockwise elliptically polarized light is transmitted through the liquid crystal layer 33 of the liquid crystal light valve 11G, it receives a phase difference due to the pretilt of the liquid crystal molecules 33B and moves to a point C on the S1-S2 plane. When the light is reflected by the pixel electrode 36 of the liquid crystal light valve 11G and then passes through the liquid crystal layer 33 again, it undergoes a phase difference due to the pretilt of the liquid crystal molecules 33B and moves to point D to become counterclockwise elliptically polarized light . Next, the counterclockwise elliptically polarized light moves to the point E by transmitting through the O plate 54. Here, when the point E coincides with the point A, the counterclockwise elliptically polarized light returns to linearly polarized light, and the front phase difference is completely compensated. This state is ideal in all the image forming optical systems 3R, 3G, and 3B. In this state, the black floating is completely suppressed, and the display contrast is maximized. Since the front phase difference is discussed here, the C plate 53 has no effect.

However, in practice, the wavelength is different for R, G, and B, and the liquid crystal and the O plate have wavelength dispersion in the refractive index anisotropy. The point E does not coincide with the point A in blue light. For example, the phase difference compensation by the O plate 54 is optimized so that the ideal state shown in FIG. 8 is obtained with green light as a reference, and the front phase difference value of the O plate 54 in the red light image forming optical system 3R is set to green. It is assumed that the front phase difference value of the O plate 54 in the light image forming optical system 3G is set. At this time, as shown in FIG. 10A, the red light has a longer moving distance from the point A to the point B due to the action of the O plate 54 on the Poincare sphere than the wavelength of the red light is green. And the refractive index anisotropy of the O plate 54 are overlapped by the influence of wavelength dispersion, which is shorter than that of green light. Next, the moving distance from the point B to the point C and the moving distance from the point C to the point D due to the action of the liquid crystal layer 33 are also shorter than the green light. However, since it is not the optimum value, the arrival point of the point C is not the optimum value as shown in FIG. Next, the moving distance from the point D to the point E due to the action of the O plate 54 is shorter than that of green light. As a result, in the case of red light, the point E does not return to the position of the point A. Therefore, in this state, the black float cannot be suppressed, and the display contrast decreases.
9 to 11 shown below represent the Poincare sphere as a circle projected on the S2-S3 plane when the surface of the sphere is viewed from the direction of the axis S1.

  Further, it is assumed that the front phase difference value of the O plate 54 in the blue light image forming optical system 3B is matched with the front phase difference value of the O plate 54 in the green light image forming optical system 3G. At this time, as shown in FIG. 11A, the moving distance from the point A to the point B due to the action of the O plate 54 on the Poincare sphere is longer than that in the case of green light. Next, the moving distance from the point B to the point C and the moving distance from the point C to the point D due to the action of the liquid crystal layer 33 are longer than in the case of green light. However, since it is not the optimum value, the arrival point of the point C is not the optimum value as shown in FIG. The moving distance from the point D to the point E due to the action of the O plate 54 is longer than that in the case of green light. As a result, in the case of blue light, the point E does not return to the position of the point A. Therefore, in this state, the black float cannot be suppressed, and the display contrast decreases.

  Here, when the front phase difference value of the O plate 54 is changed in the direction of increasing, the point A to the point B on the same curve connecting the point A and the point B on the Poincare sphere as shown in FIG. The travel distance to becomes longer. On the other hand, when the front phase difference value of the O plate 54 is changed in the direction of decreasing, the moving distance from the point A to the point B is shortened on the same curve connecting the point A and the point B on the Poincare sphere.

  In accordance with the above principle, the front phase difference value of the O plate 54 in the red light image forming optical system 3R is set larger than the front phase difference value of the O plate 54 in the green light image forming optical system 3G. Accordingly, as shown in FIG. 10B, if the moving distance from the point A to the point B is increased so that the point C does not pass the axis S2 and is located on the axis S2, the point D is changed to the point E. Similarly, the movement distance of the point E can be increased, and the point E can be matched with the point A. In this way, it is possible to sufficiently suppress black floating caused by the red light image forming optical system 3R.

  Further, the front phase difference value of the O plate 54 in the blue light image forming optical system 3B is set smaller than the front phase difference value of the O plate 54 in the green light image forming optical system 3G. Accordingly, as shown in FIG. 11B, if the moving distance from the point A to the point B is made small so that the point C is located on the axis S2, the moving distance from the point D to the point E is the same. The point E can be made coincident with the point A. In this way, the black float caused by the blue light image forming optical system 3B can be sufficiently suppressed.

  According to the projector 1 of the present embodiment, as described above, the O plate 54 of the red light image forming optical system 3R is compared with the front phase difference value of the O plate 54 of the green light image forming optical system 3G. By setting the front phase difference value large and the front phase difference value of the O plate 54 in the blue-light image forming optical system 3B small, black float caused by all the image forming optical systems 3R, 3G, and 3B is sufficiently obtained. It can be suppressed and the contrast can be improved as compared with the prior art.

In order to verify the effect of this embodiment, the present inventor performed a simulation of contrast change when the front phase difference value of the O plate was changed.
As simulation conditions, the cell thickness of the liquid crystal light valve is 2.4 μm, the retardation (Δn · d) of the liquid crystal layer is 0.29, the wavelength dispersion of the liquid crystal layer is 1.08, and the pretilt angle of the liquid crystal layer is 4.5 degrees. The wavelength dispersion of the O plate was 1.15. The results are shown in [Table 1].

  As shown in Table 1, when the angle θ formed by the slow axis of the O plate with respect to the PBS transmission axis is 3 degrees, the front phase difference value of the O plate in all image forming optical systems is unified at 15.0 nm. When the contrast in the green light image forming optical system is 100, the contrast in the red light image forming optical system is lowered to 99, and the contrast in the blue light image forming optical system is lowered to 91. On the other hand, the front phase difference value of the O plate in the image forming optical system for red light is 15.4 nm, the front phase difference value of the O plate in the image forming optical system for green light is 15.0 nm, and the image formation for blue light is performed. When the front retardation value of the O plate in the optical system is 14.1 nm, the contrast can be set to 100 in all the image forming optical systems.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS.
The basic configuration of the projector of the present embodiment is the same as that of the first embodiment, and only the phase difference compensation method in each image forming optical system is different from that of the first embodiment. Therefore, only this part will be described below.

  In the present embodiment, the azimuth angle of the slow axis of the O plate 54 of the phase difference compensation plate 12 in each of the image forming optical systems 3R, 3G, 3B is different. Here, the azimuth angle of the slow axis of the O plate 54 means an angle formed by the slow axis of the O plate 54 with respect to the transmission axis of the PBS 10, and is simply referred to as a slow axis angle in the following description. Specifically, the slow axis angle of the O plate 54 in the red light image forming optical system 3R is set to 9.4 degrees, for example. The slow axis angle of the O plate 54 in the green light image forming optical system 3G is set to 9.1 degrees, for example. The slow axis angle of the O plate 54 in the blue light image forming optical system 3B is set to 8.5 degrees, for example.

For example, the phase difference compensation by the O plate 54 is optimized based on the green light, and the slow axis angle of the O plate 54 in the red light image forming optical system 3R is set to the O plate 54 in the green light image forming optical system 3G. It is assumed that the slow axis angle is matched. At this time, as shown in FIG. 13A, the movement distance from the point A to the point B by the action of the O plate 54 on the Poincare sphere is that the red wavelength is longer than the green wavelength. The influence of chromatic dispersion overlaps with the refractive index anisotropy of the light and becomes shorter than that of green light. The moving distance from the point B to the point C and the moving distance from the point C to the point D due to the action of the liquid crystal layer 33 are longer than in the case of green light. However, since it is not the optimum value, the arrival point of the point C is not the optimum value as shown in FIG. The moving distance from the point D to the point E due to the action of the O plate 54 is shorter than that of green light. As a result, in the case of red light, the point E does not return to the position of the point A. Therefore, in this state, the black float cannot be suppressed, and the display contrast decreases.
12 to 14 shown below represent the Poincare sphere as a circle projected on the S2-S3 plane as seen from the direction of the axis S1.

  Further, it is assumed that the slow axis angle of the O plate 54 in the blue light image forming optical system 3B is matched with the slow axis angle of the O plate 54 in the green light image forming optical system 3G. At this time, as shown in FIG. 14A, the moving distance from the point A to the point B due to the action of the O plate 54 on the Poincare sphere becomes longer than in the case of green light. Next, the moving distance from the point B to the point C and the moving distance from the point C to the point D due to the action of the liquid crystal layer 33 are longer than in the case of green light. However, since it is not the optimum value, the arrival point of the point C is not the optimum value as shown in FIG. Next, the moving distance from the point D to the point E due to the action of the O plate 54 becomes longer than in the case of green light. As a result, in the case of blue light, the point E does not return to the position of the point A. Therefore, in this state, the black float cannot be suppressed, and the display contrast decreases.

  Here, when the O plate 54 is rotated in the plane to change the slow axis angle of the O plate 54 so as to increase, a curve connecting points A and B on the Poincare sphere as shown in FIG. The curve connecting point D and point E changes to a shape extending long in the direction of the axis S3. On the other hand, when the slow axis angle of the O plate 54 is changed in the direction of decreasing, the curve connecting the points A and B and the curve connecting the points D and E on the Poincare sphere are in the direction of the axis S2 (see FIG. 12 (lateral direction at 12).

  According to the above principle, the slow axis angle of the O plate 54 in the red light image forming optical system 3R is set larger than the slow axis angle of the O plate 54 in the green light image forming optical system 3G. As a result, as shown in FIG. 13B, the shape of the curve connecting point A and point B and the point D and point E are connected so that point C does not pass through axis S2 and is located on axis S2. If the shape of the curve is changed, the point E can coincide with the point A. In this way, it is possible to sufficiently suppress black floating caused by the red light image forming optical system 3R.

  Further, the slow axis angle of the O plate 54 in the blue light image forming optical system 3B is set smaller than the slow axis angle of the O plate 54 in the green light image forming optical system 3G. As a result, as shown in FIG. 14B, the shape of the curve connecting point A and point B and the shape of the curve connecting point D and point E are changed so that point C is positioned on axis S2. Then, the point E can be matched with the point A. In this way, the black float caused by the blue light image forming optical system 3B can be sufficiently suppressed.

  According to the projector of this embodiment, as described above, the slowness of the O plate 54 in the red light image forming optical system 3R with respect to the slow axis angle of the O plate 54 in the green light image forming optical system 3G. By increasing the phase axis angle and setting the slow axis angle of the O plate 54 in the blue light image forming optical system 3B to be small, black floating caused by all the image forming optical systems 3R, 3G, and 3B is sufficiently suppressed. Therefore, the contrast can be improved as compared with the conventional case. In the present embodiment, since it is not necessary to change the front phase difference value of the O plate 54, the same phase difference compensation plate 12 can be used in all the image forming optical systems 3R, 3G, 3B. When the phase difference compensation plate 12 is fixed to the housing 50, only the angle of the phase difference compensation plate 12 (in-plane rotation angle) needs to be changed, which can be easily realized.

In order to verify the effect of this embodiment, the present inventor performed a simulation of a change in contrast when the slow axis angle of the O plate was changed.
As simulation conditions, the cell thickness of the liquid crystal light valve is 2.4 μm, the retardation (Δn · d) of the liquid crystal layer is 0.29, the wavelength dispersion of the liquid crystal layer is 1.08, and the pretilt angle of the liquid crystal layer is 4.5 degrees. The wavelength dispersion of the O plate was 1.15. The results are shown in [Table 2].

  As shown in Table 2, when the front retardation value of the O plate is kept constant at 5 nm, if the slow axis angle of the O plate in all image forming optical systems is unified at 9.1 degrees, image formation for green light is performed. When the contrast in the optical system is 100, the contrast in the image forming optical system for red light is reduced to 99, and the contrast in the image forming optical system for blue light is decreased to 91. On the other hand, the slow axis angle of the O plate in the image forming optical system for red light is 9.4 degrees, the slow axis angle of the O plate in the image forming optical system for green light is 9.1 degrees, and for blue light When the slow axis angle of the O plate in the image forming optical system is set to 8.5 degrees, the contrast can be set to 100 in all the image forming optical systems.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the first embodiment, only the front phase difference value of the O plate in each image forming optical system is made different, and in the second embodiment, only the slow axis angle of the O plate in each image forming optical system is made different. By combining these configurations, both the front phase difference value and the slow axis angle of the O plate in each image forming optical system may be made different. According to this configuration, even if either one of the front phase difference value and the slow axis angle of the O plate is varied within a practically adjustable range, even if the phase difference compensation is insufficient, It is possible to sufficiently suppress the float and improve the contrast.

  In the above embodiment, the phase difference compensating plate 12 having the configuration shown in FIG. 5A is used. However, as shown in FIG. (C plate) 53A may be formed, and a phase difference compensation plate 56 formed by laminating a C plate (negative C plate) 53B and an O plate 54 in this order on the other surface may be used.

  In that case, the substrate is arranged so that the optical characteristics of the C plate (negative C plate) 53A and the C plate (negative C plate) 53B are the same as those of the C plate 53 shown in FIG. C plate 53 </ b> A and C plate 53 </ b> B are respectively formed on 52. Thus, the C plate 53A and the C plate 53B can be regarded as one C plate 53. Although not shown, the C plate and the O plate in FIG. 5B are exchanged, and the C plate and the O plate are stacked in this order on one surface of the substrate 52, and the O plate is formed on the other surface. You may use the phase difference compensation board which formed the plate. Also in this case, the optical characteristics of the two O plates sandwiching the substrate 52 are made to be the same as those of the O plate 54 shown in FIG.

Further, a C plate 53 and an O plate 54 are formed on one substrate 52, and instead of the phase difference compensating plate 12 formed by integrating them, as shown in FIG. A C plate 53 may be formed, and another substrate 52B having an O plate 54 may be used. That is, these may be combined and used as one phase difference compensation plate 57.
In addition, the material, shape, number, arrangement, and the like of the various structural members of the projector are not limited to the above-described embodiment, and can be changed as appropriate.

  DESCRIPTION OF SYMBOLS 1 ... Projector, 2 ... Illuminating device, 3R, 3G, 3B ... Image formation optical system, 4 ... Color composition element (color composition optical system), 5 ... Projection optical system, 11R, 11G, 11B ... Liquid crystal light valve, 12, 56, 57... Phase difference compensation plate, 53, 53A, 53B... C plate (first phase difference compensation layer), 54... O plate (second phase difference compensation layer).

Claims (4)

A lighting device that emits a plurality of colored lights of different colors;
A plurality of reflective liquid crystal light valves in a vertical alignment mode for modulating each of the plurality of color lights;
A first retardation compensation layer provided between the illumination device and each of the liquid crystal light valves, the optical axis of which has a negative uniaxial refractive index anisotropy along the thickness direction; A phase difference compensation plate including a second phase difference compensation layer having refractive index anisotropy;
A color synthesizing optical system that synthesizes the color light modulated by the plurality of liquid crystal light valves;
A projection optical system that projects the light synthesized by the color synthesis optical system onto a projection surface, and
Among the plurality of liquid crystal light valves, a front phase difference value of the phase difference compensator corresponding to at least one liquid crystal light valve is different from a front phase difference value of the phase difference compensator corresponding to another liquid crystal light valve. A projector characterized by that. The plurality of liquid crystal light valves are a red light modulation liquid crystal light valve, a green light modulation liquid crystal light valve, and a blue light modulation liquid crystal light valve,
A front phase difference value of the phase difference compensator corresponding to the liquid crystal light valve for red light modulation is larger than a front phase difference value of the phase difference compensator corresponding to the liquid crystal light valve for green light modulation, and the blue color A front phase difference value of the phase difference compensation plate corresponding to the light modulation liquid crystal light valve is smaller than a front phase difference value of the phase difference compensation plate corresponding to the green light modulation liquid crystal light valve. The projector according to claim 1. A lighting device that emits a plurality of colored lights of different colors;
A plurality of reflective liquid crystal light valves in a vertical alignment mode for modulating each of the plurality of color lights;
A first retardation compensation layer provided between the illumination device and each of the liquid crystal light valves, the optical axis of which has a negative uniaxial refractive index anisotropy along the thickness direction; A phase difference compensation plate including a second phase difference compensation layer having refractive index anisotropy;
A color synthesizing optical system that synthesizes the color light modulated by the plurality of liquid crystal light valves;
A projection optical system that projects the light synthesized by the color synthesis optical system onto a projection surface, and
Of the plurality of liquid crystal light valves, the azimuth angle of the slow axis in the in-plane orientation of the phase difference compensation plate corresponding to at least one liquid crystal light valve is the same as that of the phase difference compensation plate corresponding to another liquid crystal light valve. A projector characterized by being different from an azimuth angle of a slow axis in an in-plane orientation. The plurality of liquid crystal light valves are a red light modulation liquid crystal light valve, a green light modulation liquid crystal light valve, and a blue light modulation liquid crystal light valve,
A polarization beam splitter having a predetermined transmission axis is provided between the illumination device and the phase difference compensation plate,
An angle formed by the slow axis and the transmission axis of the retardation compensator corresponding to the red light modulating liquid crystal light valve is an angle formed by the retardation compensator corresponding to the green light modulating liquid crystal light valve. The angle formed between the slow axis and the transmission axis of the phase difference compensation plate corresponding to the blue light modulation liquid crystal light valve is larger than the angle formed between the phase axis and the transmission axis. The projector according to claim 3, wherein the projector is smaller than an angle formed by the slow axis and the transmission axis of the retardation compensation plate corresponding to the liquid crystal light valve.

Images